feat(lmxproxy): phase 7 — integration test project and test scenarios

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lmxproxy/tests/ZB.MOM.WW.LmxProxy.Client.IntegrationTests/SubscribeTests.cs

@@ -0,0 +1,34 @@
+using ZB.MOM.WW.LmxProxy.Client.Domain;
+
+namespace ZB.MOM.WW.LmxProxy.Client.IntegrationTests;
+
+public class SubscribeTests : IntegrationTestBase
+{
+    [Fact]
+    public async Task Subscribe_ReceivesUpdates()
+    {
+        var received = new List<(string Tag, Vtq Vtq)>();
+        var receivedEvent = new TaskCompletionSource<bool>();
+
+        var subscription = await Client!.SubscribeAsync(
+            new[] { "TestChildObject.TestInt" },
+            (tag, vtq) =>
+            {
+                received.Add((tag, vtq));
+                if (received.Count >= 3)
+                    receivedEvent.TrySetResult(true);
+            },
+            ex => receivedEvent.TrySetException(ex));
+
+        // Wait up to 30 seconds for at least 3 updates
+        var completed = await Task.WhenAny(receivedEvent.Task, Task.Delay(TimeSpan.FromSeconds(30)));
+        subscription.Dispose();
+
+        Assert.True(received.Count >= 1, $"Expected at least 1 update, got {received.Count}");
+
+        var first = received[0];
+        Assert.Equal("TestChildObject.TestInt", first.Tag);
+        Assert.NotNull(first.Vtq.Value);
+        Assert.True(first.Vtq.Timestamp > DateTime.MinValue);
+    }
+}